Ventricular assist device

ABSTRACT

Apparatus and methods are described including a tube configured to traverse a subject&#39;s aortic valve. A frame is disposed within a portion of the tube, and a plurality of winged projections are coupled to the frame. An impeller is disposed inside the tube, the impeller including proximal and distal bushings, a helical elongate element, and a spring disposed inside of the helical elongate element, the spring defining a lumen therethrough. A film of material is supported between the helical elongate element and the spring. A rigid shaft extends from the proximal bushing to the distal bushing via the lumen defined by the spring. The impeller is rotated, such as to pump blood from the subject&#39;s left ventricle to the subject&#39;s aorta. Other applications are also described.

CROSS-REFERENCES TO RELATED APPLICATIONS

The present application is a continuation of International ApplicationNo. PCT/IL2017/051158 to Tuval (published as WO 18/078615), entitled“Ventricular assist device,” filed Oct. 23, 2017, which claims priorityfrom:

U.S. Provisional Patent Application 62/412,631 to Tuval, entitled“Ventricular assist device,” filed Oct. 25, 2016; and

U.S. Provisional Patent Application 62/543,540 to Tuval, entitled“Ventricular assist device,” filed Aug. 10, 2017.

U.S. Provisional Patent Application 62/412,631 and U.S. ProvisionalPatent Application 62/543,540 are incorporated herein by reference.

FIELD OF EMBODIMENTS OF THE INVENTION

Some applications of the present invention generally relate to medicalapparatus. Specifically, some applications of the present inventionrelate to a ventricular assist device and methods of use thereof.

BACKGROUND

Ventricular assist devices are used to assist cardiac circulation, forpatients suffering from a failing heart. Most commonly aleft-ventricular assist device is applied to a defective heart, in orderto assist left-ventricular functioning. In some cases, aright-ventricular assist device is used, in order to assistright-ventricular functioning.

SUMMARY OF EMBODIMENTS

In accordance with some applications of the present invention, animpeller includes a helical elongate element, a spring that is disposedinside of, and coaxially with, the helical elongate element, and a filmof material supported between the helical elongate element and thespring. For some applications, the impeller comprises a portion of aventricular assist device configured to assist ventricular functioningof a subject, e.g., a left-ventricular assist device is configured toassist left ventricular functioning of a subject. The ventricular assistdevice typically includes an elongate tube configured to traverse thesubject's aortic valve, such that a proximal end of the tube is disposedwithin the subject's aorta and a distal end of the tube is disposedwithin the subject's left ventricle. The elongate tube includes a frameformed from a self-expandable shape-memory alloy, and a bloodimpermeable material that is disposed upon the frame. The ventricularassist device includes a pump, which typically includes the impeller anda cage disposed around the impeller. The impeller is typicallyconfigured to pump blood out of the subject's left ventricle and intothe subject's aorta, by rotating. Typically, the impeller also impedesbackflow of blood across the aortic valve, from the aorta into the leftventricle.

For some applications, the cage is integrally formed with the elongatetube such that the cage is disposed within the frame of the elongatetube at the proximal end of the elongate tube. The pump is therebydisposed within a proximal portion of the elongate tube, and alongitudinal axis of the pump is thereby aligned with a longitudinalaxis of the elongate tube. Alternatively, the cage is not integrallyformed with the elongate tube.

There is therefore provided, in accordance with some applications of thepresent invention, apparatus including:

an impeller including:

-   -   at least one helical elongate element;    -   a spring, the spring being disposed inside of, and coaxially        with, the helical elongate element; and    -   a film of material supported between the helical elongate        element and the spring.

In some applications, the impeller includes a plurality of helicalelongate elements, and the film of material is supported between theplurality of helical elongate elements and the spring, such that theimpeller defines a plurality of blades.

In some applications, when the impeller is disposed in anon-radially-constrained configuration, a pitch of the helical elongateelement varies along a length of the helical elongate element.

In some applications, when the impeller is disposed in anon-radially-constrained configuration, a pitch of the helical elongateelement is greater than 1 mm.

In some applications, when the impeller is disposed in anon-radially-constrained configuration, a pitch of the helical elongateelement is less than 20 mm.

In some applications, the impeller is configured to be placed inside ablood vessel of a subject and to pump blood through the subject's bloodvessel by the impeller rotating.

In some applications, the impeller is configured to be placed in anaorta of a subject and to pump blood from a left ventricle of thesubject, by the impeller rotating.

In some applications, the impeller is configured to be placed in aventricle of a subject and to pump blood from the ventricle, by theimpeller rotating.

In some applications, the impeller is configured to be placed in anaorta of a subject and to impede backflow of blood from the aorta into aleft ventricle of the subject.

In some applications, the impeller is configured to be radiallyconstrained by the helical elongate element and the spring being axiallyelongated, and in response to the axial elongation of the helicalelongate element and the spring, the film is configured to change shapewithout the film of material breaking.

In some applications, the apparatus further includes:

an elongate tube configured to traverse an aortic valve of a subject,such that a proximal end of the tube is disposed within an aorta of thesubject and a distal end of the tube is disposed within a left ventricleof the subject, the elongate tube including:

-   -   a frame formed from a shape-memory alloy; and    -   a blood impermeable material that is disposed upon the frame;        and

a cage disposed around the impeller,

the elongate tube being configured to be disposed around the cage andthe impeller, and the impeller being configured to pump blood from theleft ventricle to the aorta, by rotating.

In some applications, the spring, when disposed in anon-radially-constrained configuration thereof, is configured by virtueof its rigidity, to stabilize the impeller with respect to the elongatetube, during rotation of the impeller, such that a gap between an outeredge of the impeller and an inner surface of the elongate tube ismaintained.

In some applications:

the spring defines a lumen therethrough, and

the impeller further includes:

-   -   proximal and distal bushings; and    -   a rigid shaft configured to extend from the proximal bushing to        the distal bushing via the lumen defined by the spring, the        rigid shaft being configured to stabilize the impeller with        respect to the elongate tube, during rotation of the impeller,        such that a gap between an outer edge of the impeller and an        inner surface of the elongate tube is maintained.

In some applications, the cage is integrally formed with the frame ofthe elongate tube such that the cage is disposed within the frame of theelongate tube at the proximal end of the elongate tube, the impellerthereby being disposed within a proximal portion of the elongate tube,and a longitudinal axis of the impeller thereby being aligned with alongitudinal axis of the elongate tube.

In some applications, a gap between an outer edge of the impeller and aninner surface of the elongate tube is less than 1 mm.

In some applications, the gap between the outer edge of the impeller andthe inner surface of the elongate tube is less than 0.4 mm.

In some applications, the impeller is configured to be stabilized withrespect to the elongate tube, such that, during rotation of theimpeller, the gap between the impeller and the elongate tube ismaintained.

In some applications, the cage is not integrally formed with the frameof the elongate tube.

In some applications, the apparatus further includes one or more supportarms that are configured to extend from the cage to the frame of theelongate tube, and that are configured, during rotation of the impeller,to stabilize a distal end of the impeller with respect to the frame ofthe elongate tube, such that a gap between an outer edge of the impellerand an inner surface of the elongate tube is maintained.

In some applications, the support arms are configured to be slidablewith respect to the frame of the elongate tube.

In some applications, the support arms are configured to be coupled tothe frame of the elongate tube.

In some applications, the apparatus further includes a plurality ofwinged projections that are coupled to the elongate tube such thatplanes defined by the winged projections are parallel with alongitudinal axis of the elongate tube, the winged projections beingconfigured to stabilize turbulent blood flow that is generated byrotation of the impeller, by directing blood flow along a direction ofthe longitudinal axis of the elongate tube.

In some applications, the elongate tube is configured to be insertedinto a body of the subject transcatheterally, while in aradially-constrained configuration, and the winged projections areconfigured to become folded, when the elongate tube is in itsradially-constrained configuration.

In some applications, the spring defines a lumen therethrough, and theimpeller further includes:

proximal and distal bushings; and

a rigid shaft configured to extend from the proximal bushing to thedistal bushing via the lumen defined by the spring.

In some applications, the rigid shaft is configured to maintain theproximal bushing and the distal bushing aligned with each other.

In some applications, the impeller is configured to be placed into abody of a subject, and subsequent to placement of the spring inside thesubject's body, the rigid shaft is configured to be placed within thelumen defined by the spring.

In some applications, the impeller is configured to be placed into abody of a subject, and the rigid shaft is configured to be disposedwithin the lumen defined by the spring, during placement of the impellerinto the subject's body,

In some applications, the impeller further includes proximal and distalbushings, and the spring, when disposed in a non-radially-constrainedconfiguration thereof, is configured, by virtue of its rigidity, tomaintain the proximal bushing and the distal bushing aligned with eachother.

In some applications, the spring, when disposed in thenon-radially-constrained configuration thereof, is configured such thatthere are substantially no gaps between windings of the spring andadjacent windings thereto.

There is further provided, in accordance with some applications of thepresent invention, a method including:

placing within a blood vessel of a subject an impeller, the impellerincluding:

-   -   at least one helical elongate element;    -   a spring, the spring being disposed inside of, and coaxially        with, the helical elongate element; and    -   a film of material supported between the helical elongate        element and the spring; pumping blood through the subject's        blood vessel, using the impeller.

The present invention will be more fully understood from the followingdetailed description of embodiments thereof, taken together with thedrawings, in which:

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B are schematic illustrations of a ventricular assistdevice disposed in a subject's left ventricle, in accordance with someapplications of the present invention;

FIG. 2 is a schematic illustration of a pump that includes an impellerand a cage, in accordance with some applications of the presentinvention;

FIG. 3 is a schematic illustration of a frame of an elongate tube of theventricular assist device, and a cage of the impeller of the ventricularassist device, in accordance with some applications of the presentinvention;

FIGS. 4A and 4B are schematic illustrations of a ventricular assistdevice, in accordance with some additional applications of the presentinvention;

FIGS. 5A and 5B are schematic illustrations of respectivecross-sectional views of an impeller of the ventricular assist deviceshown in FIGS. 4A and 4B in accordance with some applications of thepresent invention;

FIG. 5C is a schematic illustration of a cross-sectional view of theventricular assist device shown in FIGS. 4A and 4B, in accordance withsome applications of the present invention;

FIG. 5D is a schematic illustration of the impeller of the ventricularassist device shown in FIGS. 4A and 4B in a radially-constrainedconfiguration, in accordance with some applications of the presentinvention;

FIGS. 6A and 6B are schematic illustrations of a stator of a ventricularassist device, in accordance with some applications of the presentinvention; and

FIGS. 7A, 7B, and 7C are schematic illustrations of a ventricular assistdevice that includes a centrifugal pump, in accordance with someapplications of the present invention.

DETAILED DESCRIPTION OF EMBODIMENTS

Reference is now made to FIGS. 1A and 1B, which are schematicillustrations of a ventricular assist device 20 disposed in a subject'sleft ventricle 22, in accordance with some applications of the presentinvention. The ventricular assist device includes an elongate tube 24,which traverses an aortic valve 26 of the subject, such that a proximalend 28 of the elongate tube is disposed in an aorta 30 of the subjectand a distal end 32 of the tube is disposed within left ventricle 22.The elongate tube typically includes a radially-expandable frame 34formed from a self-expandable shape-memory alloy, such as nitinol, and ablood impermeable material 36 that is disposed upon the frame. Forexample, the blood impermeable material may include polyurethane,polyester, and/or silicone. Typically, the frame provides the elongatetube with rigidity, and the blood impermeable material provides theelongate tube with blood impermeability. Further typically, the shapememory alloy of the frame is shape set such the frame assumes itstubular shape in the absence of any forces being applied to the tube.Typically, device 20 is inserted into the left ventricletranscatheterally (e.g., via the brachial artery), while the tube is ina radially constrained state. Upon being released from the catheter, thetube automatically assumes it tubular shape, due to the frame expanding.A pump 40 is disposed within the elongate tube (e.g., within a proximalportion of the elongate tube, as shown), and is configured to pump bloodthrough the elongate tube from the left ventricle into the aorta, tothereby assist left ventricular functioning.

FIG. 2 is a schematic illustration of pump 40, in accordance with someapplications of the present invention. Pump 40 typically includes aradially-expandable impeller 42 disposed inside a radially-expandablecage 44. Typically, pump 40 is inserted into the left ventricletranscatheterally, while the impeller and the cage are in radiallyconstrained configurations. The impeller and the cage typically includea shape memory alloy (such as nitinol), which is shape set such that theimpeller and the cage assume non-radially-constrained (i.e.,radially-expanded) configurations thereof in the absence of anyradially-constraining force acting upon the impeller and the cage. Thus,typically, the cage and the impeller radially expand upon being releasedfrom the distal end of the catheter via which they are inserted. Forsome applications, an engagement mechanism engages the impeller and thecage with respect to one another, such that in response to the cagebecoming radially constrained the impeller becomes radially constrained,e.g., in accordance with apparatus and methods described in described inWO 14/141284 to Schwammenthal, which is incorporated herein byreference. In general, pump 40 is generally similar to the blood pumpsdescribed in WO 14/141284 to Schwammenthal, WO 15/177793 toSchwammenthal, and/or WO 16/185473 to Schwammenthal, all of which areincorporated herein by reference. Typically, pump 40 pumps blood throughthe elongate tube from the left ventricle into the aorta, by theimpeller rotating. For some applications, a rotating cable 46 (FIG. 1B)rotates the impeller. Typically, the rotating cable is rotated by amotor (not shown) which is disposed outside the subject's body, orinside the subject's body.

For some applications, pump 40 is disposed at a proximal end of theelongate tube, such that the pump is disposed within the aorta. For someapplications, the pump is disposed at the distal end of the elongatetube, such that the pump is disposed within the subject's ventricle.

Reference is now made to FIG. 3, which is a schematic illustration offrame 34 of elongate tube 24 and cage 44 of pump 40 of ventricularassist device 20, in accordance with some applications of the presentinvention. As shown, for some applications, the cage is integrallyformed with the frame of the elongate tube, such that the cage isdisposed within the frame of the elongate tube at the proximal end ofthe elongate tube. Typically, by virtue of the cage being disposedwithin the frame of the elongate tube at the proximal end of theelongate tube, pump 40 is disposed within a proximal portion of theelongate tube, and the longitudinal axis of the pump is aligned with thelongitudinal axis of the elongate tube. For some applications, frame 34of elongate tube 24 and cage 44 are cut from a single piece (e.g., asingle tube) of a shape memory material (e.g., a shape-memory alloy,such as nitinol). Typically, by virtue of being cut from the singlepiece of the shape-memory the region of the tube in which the cage isdisposed is able to be radially compressed to a smaller diameter thanwould be possible if the cage were cut from a separate piece of theshape memory material and inserted inside the elongate tube or viceversa, ceteris paribus.

Reference is now made to FIG. 4A, which is a schematic illustration of aventricular assist device 20, in accordance with some additionalapplications of the present invention. For some applications, pump 40 isgenerally as shown in FIG. 4A. Typically, the pump includes an impeller50, which includes an outer helical elongate element 52, which windsaround a central axial spring 54, such that the helix defined by thehelical elongate element is coaxial with the central axial spring. Forsome applications, the helical elongate element and the central axialspring are made of a shape memory material, e.g., a shape memory alloysuch as nitinol. Typically, the helical elongate element and the centralaxial spring support a film 56 of a material (e.g., a polymer, such aspolyurethane, and/or silicone) therebetween. The helical elongateelement, the axial spring and the film define the impeller blade, withthe helical elongate element defining the outer edge of the impellerblade (and thereby defining the outer edge of the impeller), and theaxial spring defining the axis of the impeller blade. For someapplications, sutures (e.g., polyester sutures, not shown) are woundaround the helical elongate element, e.g., as described in WO 14/141284,which is incorporated herein by reference. Typically, the sutures areconfigured to facilitate bonding between the film of material (which istypically a polymer, such as polyurethane, or silicone) and the helicalelongate element (which is typically a shape memory alloy, such asnitinol). For some applications, sutures (e.g., polyester sutures, notshown) are wound around spring 54. Typically, the sutures are configuredto facilitate bonding between the film of material (which is typically apolymer, such as polyurethane, or silicone) and the spring (which istypically a shape memory alloy, such as nitinol).

Typically, proximal ends of both spring 54 and helical elongate element52 are coupled to a proximal bushing (i.e., sleeve bearing) 64 of theimpeller, such that the proximal ends of both spring 54 and helicalelongate element 52 are disposed at a similar radial distance from thelongitudinal axis of the impeller, as each other. Similarly, typically,distal ends of both spring 54 and helical elongate element 52 arecoupled to a distal bushing 58 of the impeller, such that the distalends of both spring 54 and helical elongate element 52 are disposed at asimilar radial distance from the longitudinal axis of the impeller, aseach other.

For some such applications, frame 34 of elongate tube 24 does notinclude a cage integrally formed therewith, as described hereinabovewith reference to FIG. 3. Rather, for some such applications, a distalbushing 58 of the impeller is stabilized with respect to the elongatetube, by means of one or more support arms 60 that extend radiallyoutwardly from the distal bushing of the impeller to frame 34 ofelongate tube 24. As shown in FIG. 4A, for some applications, thesupport arms are not coupled to frame 34 of the elongate tube, but areconfigured to engage an inner surface of the elongate tube, to therebystabilize the distal bushing of the impeller with respect to theelongate tube. For such applications, the support arms are typicallyconfigured to be moveable with respect to the elongate tube, by thesupport arms sliding along the inner surface of the elongate tube.Alternatively, even if the support arms are not integrally formed withframe 34 of the elongate tube, the support arms are coupled to frame 34of the elongate tube (e.g., via welding, suturing, and/or an adhesive),such that, at least at the locations at which the support arms arecoupled to the frame of the elongate tube, the support arms cannotundergo motion relative to the elongate tube. Further alternatively, thedevice includes support arms that are integrally formed with frame 34 ofthe elongate tube, as shown in FIG. 4B.

Reference is now made to FIG. 4B, which is a schematic illustration ofdevice 20, the device including support arms 59, which are integrallyformed with frame 34 of the elongate tube 24, the support arms beingcoupled to frame 34 at coupling points 61, in accordance with someapplications of the present invention. Typically, the support arms areconfigured to extend from the distal bushing of the impeller to thecoupling points, and are configured to thereby stabilize the distalbushing of the impeller with respect to the elongate tube.

With respect to device 20 as shown in FIGS. 4A-B, it is noted that forsome applications, impeller 50 is disposed at a proximal end of theelongate tube, as shown, such that, during use of device 20, theimpeller is disposed within the aorta, and pumps blood from the leftventricle into the aorta by rotating within the aorta. For someapplications (not shown), the impeller is disposed at the distal end ofthe elongate tube, such that, during use of device 20, the impeller isdisposed within the ventricle, and pumps blood out of the ventricle, byrotating within the ventricle. In general, in the context of the presentapplication, the term “blood vessel” should be interpreted as includinga ventricle. Similarly, an impeller that is described as being placedwithin a blood vessel, should be interpreted as including an impellerthat is placed within a ventricle.

Reference is now made to FIGS. 5A and 5B, which are schematicillustrations of cross-sectional views of impeller 50, respectivelyperpendicularly to the longitudinal axis of the impeller, and along thelongitudinal axis of the impeller, in accordance with some applicationsof the present invention. Reference is also made to FIG. 5C, which is aschematic illustration of a cross-sectional view of ventricular assistdevice 20 along the longitudinal axis of the device, in accordance withsome applications of the present invention. As shown in FIG. 5B forexample, spring 54 defines a lumen 62 therethrough. For someapplications, a rigid shaft 63 is disposed along the lumen at least fromproximal bushing 64 of the impeller to distal bushing 58. The rigidshaft is configured to impart rotational motion from the proximalbushing to the distal bushing, and/or to maintain the distal bushing andthe proximal bushing aligned with each other and aligned with thelongitudinal axis of the elongate tube. Alternatively or additionally,spring 54 itself acts as a shaft. Thus, for some applications, thespring imparts rotational motion from the proximal bushing to the distalbushing, and/or maintains the distal bushing and the proximal bushingaligned with each other and aligned with the longitudinal axis of theelongate tube. For some such applications, the spring is configured suchthat, when the spring is disposed in a non-radially-constrainedconfiguration, there are substantially no gaps between windings of thespring and adjacent windings thereto.

Reference is now made to FIG. 5D, which is a schematic illustration ofimpeller 50 in a radially constrained (i.e., axially-elongated)configuration, in accordance with some applications of the presentinvention. Typically, pump 40 is inserted into the left ventricletranscatheterally, while impeller 50 is in its radially constrainedconfiguration. As shown, in the radially constrained configuration, bothhelical elongate element 52 and central axial spring 54 become axiallyelongated, and radially constrained. Typically film 56 of the material(e.g., silicone) changes shape to conform to the shape changes of thehelical elongate element and the axial support spring, both of whichsupport the film of material. Typically, using a spring to support theinner edge of the film allows the film to change shape without the filmbecoming broken or collapsing inwardly onto a shaft disposed withinlumen 62, due to the spring providing a large surface area to which theinner edge of the film bonds. For some applications, using a spring tosupport the inner edge of the film reduces a diameter to which theimpeller can be radially constrained, relative to if, for example, arigid shaft was to be used to support the inner edge of the film, sincethe diameter of the spring itself can be reduced by axially elongatingthe spring. As described hereinabove and as shown in FIG. 5C, for someapplications, rigid shaft 63 is disposed along lumen 62 (defined byspring 54) at least from proximal bushing 64 of the impeller to distalbushing 58. For some applications, the rigid shaft is disposed insidethe lumen even during the transcatheteral insertion of the impeller intothe subject's left ventricle. Alternatively, the rigid shaft is advancedinto lumen 62 once the impeller has already been released from theinsertion catheter, and is disposed inside with subject's ventricle.

Referring again to FIG. 5A, typically there is a gap G, between theouter edge of the impeller and the inner surface of elongate tube 24,even at a location at which the span of the impeller is at its maximum.For some applications, it is desirable that the gap between the outeredge of the blade of the impeller and elongate tube 24 be relativelysmall, in order for the impeller to efficiently pump blood from thesubject's left ventricle into the subject's aorta. However, it is alsodesirable that a gap between the outer edge of the blade of the impellerand elongate tube 24 be maintained, for example, in order to reduce arisk of hemolysis. For some applications, the gap G between the outeredge of the impeller and the inner surface of elongate tube 24, at thelocation at which the span of the impeller is at its maximum, is greaterthan 0.05 mm (e.g., greater than 0.1 mm), and/or less than 1 mm (e.g.,less than 0.4 mm), e.g., 0.05 mm-1 mm, or 0.1 mm-0.4 mm). As describedhereinabove, for some applications, distal bushing 58 of the impeller isstabilized with respect to the elongate tube, by means of one or moresupport arms 60, or support arms 59. For some applications, bystabilizing distal bushing 58 of the impeller with respect to theelongate tube, even a relatively small gap between the outer edge of theblade of the impeller and elongate tube 24 (e.g., a gap that is asdescribed above) is maintained, during rotation of the impeller.Alternatively or additionally, a rigid shaft is inserted along the axisof the impeller via lumen 62 defined by spring 54, and the rigid shaftstabilizes distal bushing 58 of the impeller with respect to theelongate tube, such that even a relatively small gap between the outeredge of the blade of the impeller and elongate tube 24 (e.g., a gap thatis as described above) is maintained, during rotation of the impeller.Further alternatively or additionally, spring 54 is sufficiently rigidas to stabilize distal bushing 58 of the impeller with respect to theelongate tube, such that even a relatively small gap between the outeredge of the blade of the impeller and elongate tube 24 (e.g., a gap thatis as described above) is maintained, during rotation of the impeller.

Typically, the pitch of helical elongate element 52, when impeller 50 isin a non-radially-constrained configuration (e.g., inside the subject'sventricle), is greater than 1 mm (e.g., greater than 6 mm), and/or lessthan 20 mm (e.g., less than 10 mm). Typically, ceteris paribus, thegreater the pitch of the helical elongate element (and therefore theimpeller blade), the greater the blood flow that is generated by theimpeller. Therefore, as described, the pitch of the helical elongateelement 52, when impeller 50 is in the non-radially-constrainedconfiguration, is typically greater than 1 mm (e.g., greater than 6 mm).On the other hand, it is typically desirable that the impeller occludesbackflow from the subject's aorta into the subject's left ventricleduring diastole. Ceteris paribus, it is typically the case that thesmaller the pitch of the helical elongate element (and therefore theimpeller blade), the greater the occlusion that is provided by theimpeller. Therefore, as described, the pitch of the helical elongateelement 52, when impeller 50 is in the non-radially-constrainedconfiguration, is typically less than 20 mm (e.g., less than 10 mm).

For some applications, the pitch of the helical elongate element (andtherefore the impeller blade) varies along the length of the helicalelongate element, at least when the impeller is in anon-radially-constrained configuration. Typically, for suchapplications, the pitch increases from the distal end of the impeller(i.e., the end that is inserted further into the subject's body, andthat is placed upstream with respect to the direction of antegrade bloodflow) to the proximal end of the impeller (i.e., the end that is placeddownstream with respect to the direction of antegrade blood flow), suchthat the pitch increases in the direction of the blood flow. Typically,the blood flow velocity increases along the impeller, along thedirection of blood flow. Therefore, the pitch is increased along thedirection of the blood flow, such as to further accelerate the blood.

For some applications (not shown), impeller 50 is generally as shown inFIGS. 4A-5D, but the impeller includes a plurality of helical elongateelements. For example, the impeller may include two or three helicalelongate elements. Typically, the film of material is supported betweenthe plurality of helical elongate elements and the spring, such that theimpeller defines a plurality of blades. Typically, the number ofimpeller blades corresponds to the number of helical elongate elementsthat are disposed upon the impeller, e.g., as is generally described inWO 14/141284 to Schwammenthal, which is incorporated herein byreference.

Reference is now made to FIGS. 6A and 6B, which are schematicillustrations of a stator 65 of ventricular assist device 20, inaccordance with some applications of the present invention. FIG. 6Bshows the stator in the absence of some other elements of theventricular assist device, for illustrative purposes. For someapplications, as shown, stator 65 is disposed within a proximal portionof frame 34 of elongate tube 24. Typically, the stator includes aplurality of (e.g., more than 2, and/or less than 8) winged projections66 that, when device 20 is in a non-radially constrained configuration,extend from frame 34, and that are made of a flexible material, e.g., apolymer, such as polyurethane, and/or silicone. The winged projectionsare typically configured to define planes that are parallel to thelongitudinal axis of the elongate tube, and are thereby configured tostabilize turbulent blood flow that is generated by the impeller, bydirecting blood flow along the direction of the longitudinal axis of theelongate tube.

It is noted that, as shown in FIG. 6A, typically elongate tube 24includes blood impermeable material 36 that is disposed upon frame 34 ofthe tube. For example, the blood impermeable material may includepolyurethane, polyester, or silicone, as described hereinabove. It isnoted that, typically, the elongate tube includes the blood impermeablematerial, even though, for illustrative purposes, the blood impermeablematerial of the tube is not shown in all of the figures of the presentapplication.

As shown in FIG. 6B, for some applications, sutures 68 are wound aroundportions of frame 34, in order to facilitate coupling between the wingedprojections and frame 34, in accordance with the techniques describedhereinabove. For some applications, the winged projections extend fromframe 34 to an axial support element 69. Typically, the axial supportelement is a tubular element formed of metal, plastic, and/or a polymer(such as polyurethane and/or silicone). For some applications, stator 65is integrally formed with frame 34 of elongate tube 24. Alternatively oradditionally, the stator is formed separately from the elongate tube.

As described hereinabove, typically, device 20 is inserted into thesubject's ventricle transcatheterally, while elongate tube 24 is in aradially constrained state. Upon being released from the catheter, thetube automatically assumes it tubular shape, due to frame 34 of elongatetube 24 self-expanding. Typically, the stator is inserted into subject'sleft ventricle inside the elongate tube. During the insertion, thewinged projections of the stator are in folded states, and do notsubstantially increase the minimal diameter to which the elongate tubecan be radially-constrained, relative to if the tube did not contain thewinged projections. Upon frame 34 of the elongate tube expanding, thewinged projections are configured to automatically assume their wingedconfigurations, due to the winged projections being coupled to frame 34.

It is noted that, although FIGS. 1A and 1B show ventricular assistdevice 20 in the subject's left ventricle, for some applications, device20 is placed inside the subject's right ventricle, such that the devicetraverses the subject's pulmonary valve, and techniques described hereinare applied, mutatis mutandis. Alternatively or additionally, device 20and/or a portion thereof (e.g., impeller 50, even in the absence ofelongate tube 24) is placed inside a different portion of the subject'sbody, in order to assist with the pumping of blood from that portion.For example, device 20 and/or a portion thereof (e.g., impeller 50, evenin the absence of elongate tube 24) may be placed in a blood vessel andmay be used to pump blood through the blood vessel. For someapplications, device 20 and/or a portion thereof (e.g., impeller 50,even in the absence of elongate tube 24) is configured to be placedwithin the subclavian vein or jugular vein, at junctions of the veinwith a lymph duct, and is used to increase flow of lymphatic fluid fromthe lymph duct into the vein, mutatis mutandis.

Reference is now made to FIG. 7A, which is a schematic illustration of aventricular assist device 70 that includes a centrifugal pump 72, inaccordance with some applications of the present invention. Reference isalso made to FIGS. 7B and 7C, which show, respectively,three-dimensional and two-dimensional cross-sectional views of thecentrifugal pump, in accordance with some applications of the presentinvention.

For some applications, ventricular assist device assists pumping of aventricle (e.g., left ventricle 22) by using centrifugal pump to pumpblood from the subject's left ventricle, out of the subject body, andinto the subject's aorta 30. For some applications, a catheter 74 isinserted into the subject's vasculature that extends from centrifugalpump 72 to the subject's ventricle. As shown in FIGS. 7B and 7C,typically, catheter 74 defines concentric tubes 76 and 78. Blood ispumped out of the subject's left ventricle via a first one of concentrictubes (e.g., inner tube 76, as indicated by the dashed arrows indicatingthe direction of blood flow in FIG. 7C), and blood is pumped into thesubject's aorta via a second one of the concentric tubes (e.g., outertube 78, as shown in FIG. 7C). Typically, the first and second tubes areinserted into the subject's body via a single insertion point, e.g.,femoral artery 80, as shown in FIG. 7A, or via a different insertionpoint, such as the subclavian artery. For some applications, centrifugalpump 72 defines an additional tube 82, via which blood pressure ismeasured.

The scope of the present invention includes combining any of theapparatus and methods described herein with any of the apparatus andmethods described in one or more of the following applications, all ofwhich are incorporated herein by reference:

International Patent Application PCT/IL2017/051092 to Tuval (publishedas WO 18/061002), filed Sep. 28, 2017, entitled “Blood vessel tube,”which US Provisional Patent Application 62/401,403 to Tuval, filed Sep.29, 2016;

International Patent Application PCT/IL2016/050525 to Schwammenthal(published as WO 16/185473), filed May 18, 2016, entitled “Blood pump,”which claims priority from U.S. Provisional Patent Application62/162,881 to Schwammenthal, filed May 18, 2015, entitled “Blood pump;”

International Patent Application PCT/IL2015/050532 to Schwammenthal(published as WO 15/177793), filed May 19, 2015, entitled “Blood pump,”which claims priority from U.S. Provisional Patent Application62/000,192 to Schwammenthal, filed May 19, 2014, entitled “Blood pump;”

International Patent Application PCT/IL2014/050289 to Schwammenthal(published as WO 14/141284), filed Mar. 13, 2014, entitled “Renal pump,”which claims priority from (a) U.S. Provisional Patent Application61/779,803 to Schwammenthal, filed Mar. 13, 2013, entitled “Renal pump,”and (b) U.S. Provisional Patent Application 61/914,475 to Schwammenthal,filed Dec. 11, 2013, entitled “Renal pump;”

U.S. patent application Ser. No. 14/567,439 to Tuval (published as US2015/0157777), filed Dec. 11, 2014, entitled “Curved catheter,” whichclaims priority from U.S. Provisional Patent Application 61/914,470 toTuval, filed Dec. 11, 2013, entitled “Curved catheter:” and

International Patent Application PCT/IL2013/050495 to Tuval (publishedas WO 13/183060), filed Jun. 6, 2013, entitled “Prosthetic renal valve,”which claims priority from U.S. Provisional Patent Application61/656,244 to Tuval, filed Jun. 6, 2012, entitled “Prosthetic renalvalve.”

There is therefore provided, in accordance with some applications of thepresent invention, the following inventive concepts:

Inventive concept 1. Apparatus comprising:

a left ventricular assist device configured to assist left ventricularfunctioning of a subject, the left ventricular assist device comprising:

-   -   an elongate tube configured to traverse an aortic valve of the        subject, such that a proximal end of the tube is disposed within        an aorta of the subject and a distal end of the tube is disposed        within a left ventricle of the subject, the elongate tube        comprising:        -   a frame formed from a shape-memory alloy; and        -   a blood impermeable material that is disposed upon the            frame;    -   a rotatable impeller configured to pump blood from the subject's        left ventricle to the subject's aorta by rotating; and    -   a plurality of winged projections that are coupled to the        elongate tube such that planes defined by the winged projections        are parallel with a longitudinal axis of the elongate tube, the        winged projections being configured to stabilize turbulent blood        flow that is generated by rotation of the impeller, by directing        blood flow along a direction of the longitudinal axis of the        elongate tube.        Inventive concept 2. The apparatus according to inventive        concept 1, wherein the elongate tube is configured to be        inserted into a body of the subject transcatheterally, while in        a radially-constrained configuration, and wherein the winged        projections are configured to become folded, when the elongate        tube is in its radially-constrained configuration.        Inventive concept 3. A method comprising:

placing an elongate tube into a body of a subject, such that theelongate tube traverses an aortic valve of the subject, such that aproximal end of the tube is disposed within an aorta of the subject anda distal end of the tube is disposed within a left ventricle of thesubject, the elongate tube including:

-   -   a frame formed from a shape-memory alloy, and    -   a blood impermeable material that is disposed upon the frame;        and

pumping blood from the subject's left ventricle to the subject's aortaby rotating an impeller that is disposed within the elongate tube,

a plurality of winged projections being coupled to the elongate tubesuch that planes defined by the winged projections are parallel with alongitudinal axis of the elongate tube, the winged projections beingconfigured to stabilize turbulent blood flow that is generated byrotation of the impeller, by directing blood flow along a direction ofthe longitudinal axis of the elongate tube.

Inventive concept 4. The method according to claim inventive concept 3,wherein placing the elongate tube into the subject's body comprisesplacing the elongate tube into the subject's body transcatheterallywhile the elongate tube is in a radially-constrained configuration, thewinged projections being configured to become folded, when the elongatetube is in its radially-constrained configuration.Inventive concept 5. Apparatus comprising:

a left ventricular assist device configured to assist left ventricularfunctioning of a subject, the left ventricular assist device comprising:

-   -   an elongate tube configured to traverse an aortic valve of the        subject, such that a proximal end of the tube is disposed within        an aorta of the subject and a distal end of the tube is disposed        within a left ventricle of the subject, the elongate tube        comprising:        -   a frame formed from a shape-memory alloy; and        -   a blood impermeable material that is disposed upon the            frame; and    -   a pump comprising a rotatable impeller and a cage disposed        around the rotatable impeller,        -   the cage being integrally formed with the elongate tube such            that the cage is disposed within the frame of the elongate            tube at the proximal end of the elongate tube, the pump            thereby being disposed within a proximal portion of the            elongate tube, and a longitudinal axis of the pump thereby            being aligned with a longitudinal axis of the elongate tube.            Inventive concept 6. A method comprising:

placing, into a subject's body, a left ventricular assist deviceconfigured to assist left ventricular functioning of a subject, the leftventricular assist device including:

-   -   an elongate tube configured to traverse an aortic valve of the        subject, such that a proximal end of the tube is disposed within        an aorta of the subject and a distal end of the tube is disposed        within a left ventricle of the subject, the elongate tube        including:        -   a frame formed from a shape-memory alloy, and        -   a blood impermeable material that is disposed upon the            frame, and    -   a pump comprising a rotatable impeller and a cage disposed        around the rotatable impeller,        -   the cage being integrally formed with the elongate tube such            that the cage is disposed within the frame of the elongate            tube at the proximal end of the elongate tube, the pump            thereby being disposed within a proximal portion of the            elongate tube, and a longitudinal axis of the pump thereby            being aligned with a longitudinal axis of the elongate tube;            and

pumping blood from the subject's left ventricle to the subject's aortaby rotating the impeller,

Inventive concept 7. A blood pump for pumping blood from a firstlocation in a body of a subject to a second location in the subject'sbody, the blood pump comprising:

a first tube for pumping the blood away from the first location;

a second tube for pumping the blood toward to second location, the firstand second tubes being coaxial with respect to each other; and

a centrifugal pump configured to pump the blood through the first andsecond tubes.

Inventive concept 8. A method comprising:

pumping blood from a first location in a body of a subject to a secondlocation in the subject's body, by:

-   -   pumping the blood away from the first location via a first tube;    -   pumping the blood toward to second location via a second tube,        the first and second tubes being coaxial with respect to each        other; and    -   using a centrifugal pump to pump the blood through the first and        second tubes.

It will be appreciated by persons skilled in the art that the presentinvention is not limited to what has been particularly shown anddescribed hereinabove. Rather, the scope of the present inventionincludes both combinations and subcombinations of the various featuresdescribed hereinabove, as well as variations and modifications thereofthat are not in the prior art, which would occur to persons skilled inthe art upon reading the foregoing description.

1. An apparatus, comprising: a tube configured to traverse an aorticvalve of a subject, such that a proximal end of the tube is disposedwithin an aorta of the subject and a distal end of the tube is disposedwithin a left ventricle of the subject, the tube comprising ablood-impermeable material; a frame disposed within at least a portionof the tube; an impeller configured to be disposed inside the tube, theimpeller being configured to rotate such as to pump blood from the leftventricle to the aorta, and the impeller comprising: proximal and distalbushings; at least one helical elongate element; a spring, the springbeing disposed inside of the helical elongate element, and the springdefining a lumen therethrough; and a film of material supported betweenthe helical elongate element and the spring; and a rigid shaftconfigured to extend from the proximal bushing to the distal bushing viathe lumen defined by the spring.
 2. The apparatus according to claim 1,wherein the impeller is configured to be placed within the subject'sleft ventricle.
 3. The apparatus according to claim 1, wherein theimpeller comprises a plurality of helical elongate elements, and thefilm of material is supported between the plurality of helical elongateelements and the spring, such that the impeller defines a plurality ofblades.
 4. The apparatus according to claim 1, wherein, when theimpeller is disposed in a non-radially-constrained configuration, apitch of the helical elongate element varies along a length of thehelical elongate element.
 5. The apparatus according to claim 1,wherein, when the impeller is disposed in a non-radially-constrainedconfiguration, a pitch of the helical elongate element is greater than 1mm.
 6. The apparatus according to claim 1, wherein, when the impeller isdisposed in a non-radially-constrained configuration, a pitch of thehelical elongate element is less than 20 mm.
 7. The apparatus accordingto claim 1, wherein the impeller is configured to be radiallyconstrained by the helical elongate element and the spring being axiallyelongated, and wherein in response to the axial elongation of thehelical elongate element and the spring, the film is configured tochange shape without the film of material breaking.
 8. The apparatusaccording to claim 1, wherein the rigid shaft is configured to stabilizethe impeller with respect to the tube, during rotation of the impeller,such that a gap between the outer edge of the impeller and the innersurface of the tube is maintained.
 9. The apparatus according to claim1, wherein the spring, when disposed in a non-radially-constrainedconfiguration thereof, is configured such that there are substantiallyno gaps between windings of the spring and adjacent windings thereto.10. The apparatus according to claim 1, wherein the impeller and thetube are configured such that, when the impeller and the tube aredeployed within the subject, a gap between an outer edge of the impellerand an inner surface of the tube is less than 1 mm.
 11. The apparatusaccording to claim 10, wherein the impeller and the tube are configuredsuch that, when the impeller and the tube are deployed within thesubject, the gap between the outer edge of the impeller and the innersurface of the tube is less than 0.4 mm.
 12. The apparatus according toclaim 10, wherein the impeller is configured to be stabilized withrespect to the tube, such that, during rotation of the impeller, the gapbetween the outer edge of the impeller and the inner surface of the cageis maintained.
 13. The apparatus according to claim 1, furthercomprising a plurality of winged projections that are coupled to theframe and that are configured to rectify blood flow that is generated byrotation of the impeller, by directing blood flow toward a direction ofthe longitudinal axis of the tube.
 14. The apparatus according to claim13, wherein the tube is configured to be inserted into a body of thesubject transcatheterally, while in a radially-constrainedconfiguration, and wherein the winged projections are configured tobecome folded, when the tube is in its radially-constrainedconfiguration.
 15. A method, comprising: placing a tube into a body ofthe subject, such that the tube traverses an aortic valve of thesubject, such that a proximal end of the tube is disposed within anaorta of the subject and a distal end of the tube is disposed within aleft ventricle of the subject, the tube including a blood impermeablematerial, a frame being disposed within at least a portion of the tube,an impeller being disposed inside the tube, the impeller including:proximal and distal bushings; at least one helical elongate element; aspring, the spring being disposed inside of the helical elongateelement, and the spring defining a lumen therethrough; and a film ofmaterial supported between the helical elongate element and the spring,and a rigid shaft extending from the proximal bushing to the distalbushing via the lumen defined by the spring; and rotating the impeller,such as to pump blood from the subject's left ventricle to the subject'saorta.
 16. The method according to claim 15, wherein rotating theimpeller comprises rotating the impeller while the impeller is disposedinside the subject's left ventricle.
 17. The method according to claim15, wherein placing the tube into the subject's body with the impellerdisposed inside the tube comprises inserting the impeller into thesubject's body transcatheterally by axially elongating the helicalelongate element and the spring, thereby causing the film of material tochange shape, without the film of material breaking.
 18. The methodaccording to claim 15, wherein rotating the impeller comprises using therigid shaft to stabilize the impeller with respect to the tube, duringrotation of the impeller, such that a gap between an outer edge of theimpeller and an inner surface of the tube is maintained.
 19. The methodaccording to claim 15, wherein placing the tube into the subject's bodywith the impeller disposed inside the tube comprises placing the tubeinto the subject's body with the impeller disposed inside the tube, suchthat, when the impeller is deployed inside the subject's body, there aresubstantially no gaps between windings of the spring and adjacentwindings thereto.
 20. The method according to claim 15, wherein placingthe tube into the subject's body with the impeller disposed inside thetube comprises placing the tube into the subject's body with theimpeller disposed inside the tube, such that, when the impeller and thetube are deployed inside the subject's body, a gap between an outer edgeof the impeller and an inner surface of the tube is less than 1 mm. 21.The method according to claim 20, wherein placing the tube into thesubject's body with the impeller disposed inside the tube comprisesplacing the tube into the subject's body with the impeller disposedinside the tube, such that, when the impeller and the tube are deployedinside the subject's body, the gap between an outer edge of the impellerand an inner surface of the tube is less than 0.4 mm.
 22. The methodaccording to claim 20, wherein rotating the impeller comprisesstabilizing the impeller with respect to the tube, during rotation ofthe impeller, such that the gap between an outer edge of the impellerand an inner surface of the tube is maintained.
 23. The method accordingto claim 15, wherein placing the tube into the subject's body comprisesplacing the tube into the subject's body, a plurality of wingedprojections being coupled to the frame, the winged projections beingconfigured to configured to rectify blood flow that is generated byrotation of the impeller, by directing blood flow toward a direction ofthe longitudinal axis of the tube.
 24. The method according to claim 23,wherein placing the tube into the subject's body comprises placing thetube into the subject's body transcatheterally while the tube is in aradially-constrained configuration, the winged projections beingconfigured to become folded, when the tube is in itsradially-constrained configuration.